The present invention relates generally to thin, flexible stock materials, and, more particularly, to tapes and sheets including means enabling a newly formed edge to be visually apparent, thereby enhancing the ability of a user to locate the edge on a roll of such materials.
Modern adhesive tapes and flexible sheet materials are now mass-produced with a very high degree of uniformity, both in terms of thickness and color or transparency. As a result, without a dispenser, it is often very difficult to find the edge of such materials, particularly if allowed to fall back onto the outer surface of the roll once cut or torn for use.
Many different types of tape exhibit this frustrating problem, including mending tapes and packing tapes, particularly the clear varieties. One clever solution to this problem is disclosed in U.S. Pat. No. 3,537,578, simply entitled xe2x80x9cTAPE.xe2x80x9d According to this patent, a piece of tape includes a continuous marking imprinted thereon, which preferably extends diagonally from one corner of the tape to the other, or, alternatively, a wavy line is used which forms part of the repeating pattern. In both cases, after the tape is formed into a roll, the free end of the tape can be plainly visualized because the continuous line is broken and separated. It is clear from the disclosure of this patent, that the concept is not intended for use with transparent tapes, since only xe2x80x9cinsulating tapesxe2x80x9d are specifically mentioned. If applied to transparent tapes or other materials, the line might be undesirable, particularly if the layers of the material are substantially transparent.
Although certain tape structures make use of fluorescence, its use is for surface highlighting as opposed to edge-finding. Using U.S. Pat. No. 4,913,946 as an example, which is entitled xe2x80x9cFLUORESENCE ADHESIVE TAPE FOR USE AS A HIGHLIGHTER,xe2x80x9d fluorescent ink is applied to one face of the transparent film or support base, having a layer of low-tack adhesive, allowing the removal of the material from library books, and so forth, without damaging the printed matter. U.S. Pat. No. 5,693,394, entitled xe2x80x9cPRESSURE-ACTIVATED FLUORESCENT MARKING TAPE,xe2x80x9d includes an adhesive fluorescent coloring layer coated on a carrier, wherein, upon application of pressure on the back of the carrier, the coloring layer is transferred to a substrate. U.S. Pat. No. 5,707,482, entitled xe2x80x9cREMOVABLE HIGHLIGHTING TAPE,xe2x80x9d adds the feature of a dispenser having a cutting edge, further evidence that the prior art does not teach or consider the use of fluorescence or other optically-activated materials as an edge-finding feature. It is a notable, and required, feature of these highlighting tapes that they are highly colored, and this precludes their use in many applications.
Although at least one patent discloses the use of colored edges for edge-finding, this is not disclosed for use with newly-formed edges, but, rather, for use in conjunction with existing edges which are not torn or cut. This particular reference is U.S. Pat. No. 5,340,629, entitled xe2x80x9cADHESIVE TAPE,xe2x80x9d which is directed to the translucent material having an adhesive-free colored edge, enabling a health-care worker to visually discern and manipulate a tape edge even when using protective gloves. Thus, any mechanism tending to make newly formed edges on tapes or other materials more visually apparent would be welcomed by users thereof.
This invention helps to solve problems in locating the free end or edge of tapes and other thin flexible materials through the use of a substance which causes the free end or edge to become a different color, or to glow, when cut or torn, but which does not significantly change the transparent nature of the tape. In the preferred embodiment, the substance is contained within the flexible material itself, though one or more layers may be added to the material to carry the substance.
The invention may be applied to various thin, flexible materials, including adhesive tapes, food wraps and other packaging materials, and is particularly advantageous when used in conjunction with transparent materials provided in roll form, where the free end of the material may stick to, or at least fall back onto, the outer surface of the roll, causing the edge to become otherwise difficult to locate. The invention is particularly useful when applied to clear packing tapes, which tend to be extremely transparent, and are often provided without a dispenser.
In an adhesive tape embodiment, the substance added to the material is preferably a daylight fluorescent additive, such as a fluorescein dye. The backing material of the tape is preferably employed as a light pipe. Ambient illumination enters into the tape and is wavelength-shifted by the fluorescent dye to a highly visible, preferably monochromatic or near-monochromatic illumination, which exits through the free edge of the tape, causing it to glow. To enhance this effect, the sides of the tape, particularly if supplied in roll form, may be coated with an opaque or reflective material, enhancing internal reflections within the backing material to enhance the exiting of light through the free end. Also, one or more surfaces of the tape, or the adhesive, may be treated, or selected, to further enhance the scattering of light back into the tape.
A wide variety of backing materials may be used in such an embodiment, including, but not limited to cellophane, vinyl, polyester, and the like. Nor is the invention limited in terms of adhesive, and may exploit an entire range of adhesives from extremely tenacious to low-tack types of the kind used for Post-it(copyright) notes and tapes. Different daylight-fluorescent materials besides fluoresceins may also be used, and such alternative materials will be readily apparent to one of skill in the art.
In addition, as an alternative to the use of a light-carrying conduit, the substance used for edge-finding may be contained in microcapsules, such that when the tape or other material is cut or torn, the substance is exposed, causing it to fluoresce, become a different color, or otherwise become visually apparent; in some instances, as a result of interaction with oxygen, water, or other components of the ambient atmosphere. Thus, at least according to this embodiment, the invention is not limited to transparent or translucent materials.